System for lubricating and monitoring a lubricatable element

ABSTRACT

A system for lubricating at least one lubricatable element, the system having an injection head for a lubricant that is adapted to be brought into contact with the at least one lubricatable element and a mechanism for evaluating the state of the element.

The present invention is related to the field of the prospectivemaintenance of elements that may be subjected to wear and tear.

The present invention also pertains to the field of the lubrication ofsuch type elements. The elements may be part of a conveyor apparatus andfor example be of the kind of an escalator or of the kind used totransport objects into a factory or a warehouse such as for example aconveying apparatus of a line for sterilizing tinned food in a foodplant.

The devices for lubricating during operation generally comprise alubricant dispenser that is brought into contact with the element to belubricated while said element is moving, synchronization being ensuredby the fact that the device is driven by the element to be lubricated.In this respect, the French document No. 2 749 571 is known, which morespecifically finds application in escalators or moving sidewalks inwhich it ensures reliable lubrication.

This document describes an automatic lubricating device with a pluralityof pumps that are driven along a path and are provided with a carryingelement that carries a part which can be moved in translation relativeto the carrying element and can be brought into contact with alubricating fitting of a movable element for allowing injection of alubricant therein during a lubrication phase. The pumps are connectedthrough an endless connecting means. The lubricating device is driventhrough the lubricating fittings acting onto the movable parts of thepumps. During the lubricating phase, the movable part of a pump iscoaxial with the corresponding lubricating fitting as soon as themovable part and the lubricating fitting are brought into contact. Thelubricating device is comprised of a means for keeping the carryingelement of a pump in a stationary relationship with the correspondinglubricating fitting and the movable part is displaced normal to the pathof the lubricating fitting.

A lubricating system with only one single reciprocating pump alsoexists.

In the field of food products, a multitude of conveyor belts are beingused which comprise articulated members, axes and mostly rollers forrolling on a roller conveyor belt. It has been found necessary tolubricate the joints between the members and the bearings of the rollersin order to lengthen the life of the conveyor belt. Traditionally, thislubrication is performed by hand by an operator, which proved to beexpensive with respect to the time the operator needs to perform thistask and to the time the conveyor belt must be halted, which generallyrequires further machines located up- and downstream of the conveyorbelt to be stopped. Moreover, the operator may forget to lubricate oneof the elements of the conveyor belt or may inject an insufficient or anexcess quantity of lubricant, which in the first case may causeexcessive wear of the belt and in the second case the lubricant to flowout, which is disastrous with regard to the strict hygiene regulationsthe equipment of the food industry is required to comply with.

Moreover, the operating conditions are sometimes stringent because ofthe increased operating temperature, the temperature variations betweenthe periods of operation and the idle periods, generally during thenight, and because of the high humidity, more specifically in the caseof a belt installed on a sterilization machine for tinned food.Therefore, insufficient lubrication involves the risk that the beltwears rapidly which would lead to an increase in the energy losses andto excess consumption by the electric driving motor(s), that alengthening of the chain happens and, as a result thereof, that thespacing between two elements increase which, in certain applications, isfound disturbing, more specifically if an object to be transported ishung on swings that are fixed to the belt, for example in a factory formanufacturing vehicles, and finally that the tearing of the chain occurswhich would result in the conveyor apparatus having to be brought to ahalt and the surrounding machines to be stopped.

The invention suggests to eliminate the disadvantages of the prior artsystems.

The invention suggests to perform, at time settable intervals, anevaluation of the state of a conveying element without the conveyorapparatus having to be halted.

The invention suggests to provide a monitoring function in addition tothe lubricating function.

According to one aspect of the invention, the lubricating system isintended for at least one lubricatable element. The system is comprisedof a lubricant-injection head that is suited to be brought into contactwith the element at least at regular intervals. The system is comprisedof a means for evaluating the state of the element.

The injection head can be adapted to be brought into contact at least atregular intervals.

The element can be an axis that connects two chain links of a conveyorapparatus or a roller element of a conveyor apparatus.

Advantageously, the element is comprised of a receiving member adaptedto cooperate with the injection head and of an active part to belubricated and the system is comprised of a means for evaluating thestate of the active part. The receiving member discharges in the activepart.

In an embodiment of the invention the evaluation means comprises asensor for sensing the lubricant pressure. The sensor may be apiezoelectric sensor that delivers an analog voltage or current signalat the output.

In an embodiment of the invention, the sensor is disposed upstream ofthe injection head as viewed in the direction of flow of the lubricant.

The sensor is preferably disposed in a dosing chamber.

In an embodiment of the invention, the system comprises means forstoring the data delivered by the evaluation means. It is thus possibleto determine the evolution of the state of the element. In the case of aconveyor apparatus comprised of a plurality of elements of one singletype or of sometimes two or three different types, the individual stateof each element is stored so that maintenance work required for thiselement can be provided. Advantageously, at least one element is markedso that the system recognizes each element contacting the lubricatingsystem during passage thereof.

Advantageously, the system comprises an acquisition card and a computer.The acquisition card forms an interface between the evaluation means andthe computer.

In an embodiment of the invention the computer comprises computing meansadapted to deliver a pressure curve as a function of time, means forcomparing the curve with predetermined values and warning means in theevent that one of the values has been reached. The pressure curve as afunction of time may be recorded for each lubricating cycle of everyelement or at longer time intervals, such as once a day for each elementfor example. A lubricating cycle comprises a phase of preparation inwhich the injection head is brought nearer, a phase of actual injectionduring which the pressure curve as a function of time is recorded, and aphase of removal during which the pressure drop can be measured.

In an embodiment of the invention the values include the maximumpressure, the minimum pressure and the maximum pressure increase.

The present invention also suggests a system for monitoring the state ofan active part of an element, said element comprising a means forlubricating said element and a means for evaluating the state of saidelement. The evaluation means can be attached to the lubrication means.

Advantageously, the element belongs to a conveyor belt which iscomprised of a plurality of identical elements.

The invention also suggests a method for monitoring the state of anactive part of an element by which a lubricant is injected into theelement and the state of the element is evaluated.

More specifically, the state of an axis to be lubricated is monitored,lubricant is injected into a space that is in contact with the axis andis provided for this purpose, and a variable representing the state ofthe axis is measured during injection. The variable may be the injectionpressure of the lubricant. It is for example a matter of course that ifthe lubrication port is clogged, the pressure will adopt excessivelyhigh values. Conversely, if the axis shows considerable wear performancewith a certain amount of play relative to the elements which itconnects, the lubricant will be capable of flowing more easily and thepressure of the lubricant during injection will be extremely low.

The present invention will be understood better upon reading the nonrestrictive detailed description of an embodiment, given by way ofexample only, with reference to the appended drawings wherein:

FIG. 1 is a schematic view of the system according to an exemplaryembodiment of the invention;

FIGS. 2 to 4 show examples of pressure curves as a function of timeduring a lubrication cycle;

FIG. 5 is a view of a window for configuring the parameters of theevaluation;

FIG. 6 is a view of a window for configuring the parameters of theconveyor apparatus;

FIG. 7 is a view of a window with a summary of the evaluations performedfor all of the elements of a conveyor apparatus;

FIG. 8 is a view of a window with a summary in which the elements areclassified according to their state; and

FIG. 9 is a partial sectional view of an example of a dosing pump thatmay be provided with a pressure sensor and, if necessary, with atemperature sensor mounted thereon; and

FIG. 10 is a view similar to FIG. 9 showing the dosing pump inoperation.

From FIG. 1 it can be seen that the system comprises an injection head 1which is provided with a cavity 2 appropriate to cooperate with alubricating fitting, a lubricating pump 3, preferably configured to be adosing pump, which is adapted to pump a given dosing amount of lubricantupon each actuation, a pump-carrying cradle 4 and a rail 5 intended tobe mounted in a fixed position.

The pump 3 can be moved in translation relative to the cradle 4 in thedirection as shown by the arrow 6. For this purpose, an electrical orpneumatic actuation member may be provided but has not been illustratedherein for purposes of clarity. The cradle 4 is movable relative to therail 5 in the direction as shown by the arrow 7. The motion oftranslation of the cradle 4 relative to the rail 5 may either be ensuredby an actuation member (not shown) or by a device for temporarilyblocking the motion of the cradle 4 on a conveyor apparatus. Such ablocking means may be comprised of a movable pin which in one positionengages in a space through which an element of the conveyor apparatusextends during the displacement thereof. When the pointer is movedbackward, the cradle 4 is allowed to return to its initial position bythe action of gravity and/or of a spring system and/or a counterweightand/or a pneumatic or electrical actuation member.

The system further comprises an control unit 8 intended to perform thefunction of controlling the actuation member of the pump 3 and themovement of the cradle 4. The pump 3 is equipped with a pressure sensor9 that is also connected to the control unit 8. The pressure sensor 9can for example be an analog or a piezoresistive sensor and can supplyan output current that is proportional to the measured pressure.

The conveyor apparatus with which the system is to cooperate isindicated at 10 and has been represented in parts only. The conveyorapparatus 10 comprises a plurality of connecting elements 11 that aregenerally oriented in the direction of their displacement, a pluralityof axes 12 that are generally oriented in the direction transverse totheir displacement and join the connecting elements 11 together, and aplurality of rollers 13 that are mounted on the end portion of the axes12 in order to allow the conveyor apparatus 10 to be carried by astationary roller belt (not shown). In order to ensure lubrication ofthe elements of the conveyor apparatus 10 that are displaced relative toeach other, more specifically on the end portions of the conveyorapparatus as viewed in the longitudinal direction, the end portion ofeach axis 12 is connected to a lubricating fitting 14 that extendsbeyond the corresponding roller 13 and is configured as a protuberancecapable to cooperate with the cavity 2 of the injection head 1. Theelement corresponding to the lubricating fitting could also be hollowand capable to cooperate with an injection head provided with aprotuberance.

In the shown example, the part of the conveyor apparatus 10 that islocated adjacent the system is displaced in the direction of arrow 15,the return of the conveyor apparatus is not shown. For the purpose oflubricant transfer between the pump 3 and the lubricating fitting 14 inthis phase, the injection pump 3 is capable of coming into contact withthe lubricating fitting 14 as the conveyor apparatus 10 is being moved,and then parting from the lubricating fining 14 to move back in thedirection opposite arrow 15 and to come into contact with anotherlubricating fitting 14 that may be the following lubricating fitting ora lubricating fitting located farther away. These steps are controlledby the control unit 8.

The system further comprises a computer 16 provided with a monitor 17, akeyboard 18 and a mouse 19 and, not shown, with at least one processor,a read-only memory, a working memory and a bus for communication betweensaid elements. A data transmission connection 20, which can be anADC-type or an RS 232-type, serves as an interface between the controlunit 8 and the computer 16. The computer 16 has a program which isstored in the read-only memory and is capable of processing dataoriginating from the control unit 8 which regard on the one hand thepressure data delivered by the sensor 9 and on the other hand thecontrol and verifying data originating from the control unit 8 itself.

From the FIGS. 2 through 4 it can be seen that the programme permits toanalyze and interpret the pressure data as a function of time.

FIG. 2 shows a window intended to be displayed on the monitor 17 of thecomputer 16. The window displays a curve that shows the time inmilliseconds on the abscissa and the pressure in bar on the ordinate.The time 0 is delivered by the control unit 8 at contact between theconveyor apparatus 10 and the injection head 2. The vertical bar 21corresponds to a signal sent by the control unit 8 for the start of thedisplacement of the cradle 4. The vertical bar 22 corresponds to thetime of the return motion of pump 3, said return motion being controlledby the control unit 8. The vertical bar 23 corresponds to the returnmotion of the blocking pin that permits to synchronize the motion of thecradle 4 and the motion of the conveyor apparatus 10.

The pressure curve as a function of time consists of a plurality ofphases:

-   -   phase 24—constant pressure that begins at time t=0 and extends        beyond the vertical bar 21. The cradle 4 moves synchronous to        the conveyor apparatus 10. The injection head 2 gets near the        corresponding lubricating fitting 14.    -   phase 25—fast increase in pressure that corresponds to the        beginning of the lubricant transfer from the pump 3 to the        conveyor apparatus 10.    -   phase 26—substantially constant, increased pressure for a period        of time that is here slightly shorter than 20 ms.    -   phase 27—too short to be suitably shown in FIG. 2, it generally        corresponds to a peak at the end of phase 26.    -   phase 28—pressure drop, in the present case of bearings, which        corresponds to the end of the lubricant transfer, the        pre-defined volume having already been transferred during the        previous phases.    -   phase 29—corresponding to the time after vertical bar 22 and        after refilling the dose of the dosing pump 3, therefore        pressure drop until a value is reached that is smaller than that        of phase 24, until reaching phase 30 that constitutes the lowest        pressure value followed by phase 31 of stability and of slight        increase in pressure.

Moreover the information for the identification of the axis thelubrication curve of which is displayed appears on the top left cornerof the screen above the window. The current axis is axis No. 3 of aconveyor apparatus with 2080 axes. The number of revolutions of theconveyor apparatus from the beginning of the measurement is alsodisplayed. In the example shown, it is the first revolution. On theright side of the window a colour code is displayed depending on whetherthe state of the axis the curve of which is displayed is satisfactory,non-satisfactory or to be monitored particularly. To the right of thewindow, there are displayed the injection time, which is confinedbetween the bars 21 and 22, and the transfer time, which is defined asthe time during which the pressure is greater than a predeterminedpercentage, e.g., 90% of the maximum pressure observed during the phases26 and 27. The gradient given in bar/second is derived from the curve inphase 25.

The term “cradle” designates the time the cradle 4 needs to return toits initial position so that it is ready for the next injection oflubricant. The term “injection” is the maximum injection pressure on thedisplayed curve. The term “expansion” is the minimum pressure measuredon the curve, generally during phase 30. The term “refill” is thepressure during phase 24, in other words the refill pressure of thedosing pump 3.

The minimum and maximum values of these various features are defined inorder to reliably find a curve showing an anomaly. As a matter of fact,a lubricating fitting clogged with dust or foreign matter may possiblyhave a curve showing values of transfer time, gradient, injectionpressure and expansion pressure that are too high as the dosing deviceremains filled with lubricant. A missing lubricating fitting, or even amissing axis, will be expressed by a too low gradient, a too lowinjection pressure, and a too low transfer time as well. If thelubricant reservoir connected with the dosing pump 3 is empty, theexpansion pressure will be too low because in this case nothing but airis admitted into the dosing pump 3. The refill pressure will possibly below as well.

FIG. 3 shows a window similar to that shown in FIG. 2 except the factthat the curve represents the case in which a lubricating fitting ismissing. It can be seen that the lubricating fitting of concern is thatof axis No. 7. Here, the transfer time is much shorter. Conversely, FIG.4 shows the case in which a lubricating fitting is clogged. Then, thetransfer time is too long and the injection pressure too high.

FIG. 5 shows a window that is capable to be displayed on the monitor 17of computer 16 and that permits to adjust the minimum and maximum valuesof the injection time, the transfer time, the gradient, the time neededfor the cradle to return, the injection pressure, the expansion pressureand the refill pressure. The minimum values established by the operatoror the supplier of the system appear in column 32 whereas thecorresponding maximum values appear in column 34. The minimum valuesmeasured for a given conveyor apparatus appear in column 33 and themaximum values measured in column 35.

FIG. 6 shows a window that permits to enter data about the conveyorapparatus such as for example the resting time between two lubricatingsequences, the number of members, the injection time, the increment P,meaning that lubrication is performed on every p^(th) lubricatingfitting only, which has been found out to be particularly useful in thecase of fast moving conveyor apparatuses in which it is more convenientto lubricate every p^(th) lubricating fitting only and to have it make Prevolutions before a complete lubrication. Further, the number ofcradles or carriers as well as other parameters that have not beendiscussed herein also appear.

FIG. 7 shows a window intended to be displayed on the monitor 17 ofcomputer 16 for showing the summary of the results of measurement. Theseven features mentioned herein above are displayed in column 36. Thepredetermined minimum values appear in column 37. The predeterminedmaximum values appear in column 38. The minimum values measured appearin column 39, the maximum values measured in column 40 and the meanvalues measured in column 41. A warning indicator appears in column 42,the color of which is green as long as the value is satisfactory, orangeif the result indicates that monitoring is required, and red if theresults are non-satisfactory.

FIG. 8 illustrates a window with smaller dimensions that is easier todisplay on part of the monitor 17 and that summarizes the informationdisplayed in the window of FIG. 7. According to the colors explainedherein above, the axes are divided into three categories: satisfactory,to be monitored, non-satisfactory. In the case represented, no axisbelongs to the non-satisfactory or to the to-be-monitored category andthe twenty axes that have been analyzed belong to the satisfyingcategory. If one directs the pointer of the mouse onto arrow 43, a listof the axes in each category is displayed, and in displacing the pointeronto region 44 in which the number of the axis is shown, it is possibleto initiate the visual display of detailed data about the axis, forexample in the way shown in the FIGS. 2 through 4.

Advantageously, the computer 16 is connected to an Internet-typecommunication network that permits teletransmission of the datacorresponding to the windows discussed herein above. Remote monitoringof a conveyor apparatus may thus be achieved and, in the event thatparts need to be replaced, an operator may be sent with the faultlessparts or a local maintenance service may be informed that such and sucha part of such and such an axis of the conveyor apparatus needs to bereplaced soon.

With remote monitoring, a remote operator receives all the datareferring to the conveyor apparatus, analyzes the data by searching thefaults of the elements that are indicated as being in a non-satisfactorystate or in a state that needs monitoring and can send to a localmaintenance service a summary establishing the number of the element,the kind of the variable which is different from normal and the mostlikely fault as well as a suggestion for eliminating the fault.

The lubrication cycle can be optically displayed in real time, thecourse of the lubrication cycles of each element to be lubricated can beanalyzed and an information about the state thereof can be inferredtherefrom.

The control unit 8 can be readily programmed to perform lubrication atregular intervals. The computer processes the measuring data during thelubrication cycle of the elements of the conveyor apparatus and canoutput a warning message if a non-satisfactory result is obtained forone of the elements. The warning message can be displayed on the monitor17 or on a remote monitor and can be combined with an alarm sound.

The system may moreover be completed by a temperature sensor that may bedisposed in proximity to the interior space of the dosing pump 3 forsensing the temperature of the lubricant and/or in proximity to theelements of the conveyor apparatus that are to be lubricated, forexample by means of an infrared sensor located at a certain distance,for the purpose of for example shortening the lubrication cycles ifoperation takes place at a higher temperature which results in asatisfactory lubrication or conversely to lengthen the cycles ifoperation takes place at a low temperature, which results in lubricantsavings.

The system may also be connected to the control system of an electricdrive motor of the conveyor apparatus, which control system may consistof a computer, an control unit or a monitoring device, so that aninformation about the power consumed by the electric drive motor istransmitted to the computer 16 which is capable of initiating apremature lubrication cycle if the power consumption increases to exceeda predetermined value.

From the FIGS. 9 and 10 in particular it can be seen that a pump 3comprises a carrying element 50, a contact piece 51 that forms acylinder capable to move in translation relative to the carrying element50 in a direction perpendicular to the movement of said carrying element50, and a piston 52 capable to be moved in translation relative to thecontact piece 51 which is capable of coming into contact with alubricating fitting 14. At one end, the piston 52 engages a bore 53 ofthe carrying element 50 and at the other end a bore of the contact piece51. A dosing chamber 63 is formed between the piston 52 and the closedend of bore 53.

A spring 55 is disposed around the piston 52 between the carryingelement 50 and the contact piece 51. The piston 52 is provided with ahole that is oriented in the longitudinal direction and forms a channel56 for the lubricant. The channel 56 comprises a widening or chamber 57which is located on the side of the contact piece 51 and accommodates asealing ball 58 and a spring 59, the two of them forming a valve that isclosed in the position of rest (FIG. 9) and open for lubrication in theactive position (FIG. 10). Therefore, the lubricant within the chamber57 has no contact with the ambient air in the position of rest so thatit is prevented from decomposing.

The contact piece 51 comprises a tube 60 disposed in the bore 54, saidtube being adapted to come into contact with the ball 58 for displacingit relative to the piston 52, which enables the lubricant to flow to thelubricating fitting 14. The bore 53 of the carrying element 50 isconnected with a lubricant supply line 61 in order to allow filling ofthe dosing chamber 63 in the position of rest. The carrying element 50is connected to an actuation member 62, for example to a hydraulic orpneumatic cylinder, that is capable of displacing it in translation. Apressure sensor 9 is intended to measure the pressure in the dosingchamber 63.

In the position of rest (FIG. 9), the springs 55 and 59 are unloaded.The carrying element 50 and the contact piece 51 are spaced apart andthe contact piece 51 is spaced apart from the lubricating fitting 14.The ball 58 is in the locking position.

In the active position of lubrication (FIG. 10), the actuation member 62displaces the carrying element 50, the piston 52 and the contact piece51 toward the lubricating fitting 14. The contact piece 51 is stopped bythe lubricating fitting 14. The carrying element 50 continues to moveand gets near the contact piece 51 while compressing the spring 55. Theball 58 contacts the tube 60 that blocks its movement while compressingthe spring 59. The lubricant may then flow out.

Accordingly, the system permits to confirm that the lubrication issatisfactory, to acquire the parameters of the lubrication cycle and tocheck the lubrication cycle, to provide information for every chain linkor every element of a conveyor belt, to select the lubricant in the bestpossible way insofar as it is easy to perform a lubrication cycle withanother lubricant than the usual one and to analyze the pressure curvesas a function of time for each lubrication cycle, to program and complywith the changes in the parameter adjustments of the control unit, torecord and file the injection curves of each chain link for analysis.The analysis of the injection curves permits to register poorlubrication or a fault of the element (the chain link can be open,broken, clogged, and so on).

Accordingly, the system permits efficient, prospective maintenance withevery element of the conveyor apparatus being monitored, which resultsin a longer life of the conveyor apparatus and in savings of lubricant.The longer life of the conveyor apparatus is an important advantage withrespect to the costs involved in replacement and in downtime ofproduction during replacement of the conveyor apparatus.

Furthermore, the control unit may be provided with a memory large enoughto hold the pressure data measured by the pressure sensor and to permitthat an operator in charge of maintenance appears at regular but spacedintervals with a portable computer to temporarily connect it to thecontrol unit in order to transfer and analyze the data.

1. A method for lubricating and monitoring a state of a lubricatableelement during a lubrication cycle in which an injection head injectslubricant into the lubricatable element, comprising: measuring aninjection pressure of lubricant being injected into the lubricatableelement as a function of time during the lubrication cycle; registeringthe injection pressure as a variable representing the state of thelubricatable element during the lubrication cycle; and evaluating thestate of the lubricatable element as a function of the variable, whereinthe injection pressure is measured upstream of the injection head asviewed in the direction of flow of the lubricant, and the state of thelubricatable element is evaluated during injection of the lubricant byan analysis of the injection pressure as a function of time, theanalysis including an interpretation of a transfer time, the transfertime defined as a time during which the pressure is greater than apredetermined percentage of a maximum pressure observed during theinjection cycle.
 2. The method as defined in claim 1, furthercomprising, for lubrication: bringing the injection head in contact withthe lubricatable element; injecting the lubricant; detaching and theinjection head from the lubricatable element.
 3. The method as definedin claim 1, further comprising storing an individual state of aplurality of lubricatable elements.
 4. The method as defined in claim 1,wherein the lubrication cycle is shortened or lengthened depending on atemperature of the lubricant.
 5. The method as defined in claim 1,wherein a dosing pump with the injection head is moved together with thelubricatable element in a translation direction.
 6. The method asdefined in claim 5, wherein a cradle carrying the dosing pump and theinjection head is locked with the lubricatable element during movementof the lubricatable element.
 7. The method as defined in claim 1,wherein the lubricatable element is lubricated while being moved.
 8. Themethod as defined in claim 1, wherein the injection head is successivelybrought into contact with a plurality of moving lubricatable elementsthat are moved by a conveyor element.
 9. The method as defined in claim8, wherein a state of the conveyor element is evaluated at adjustabletime intervals during operation of the conveyor element.
 10. The methodas defined in claim 1, wherein the lubrication cycle is shortened if atemperature of the lubricant is increased.
 11. A method for lubricatingand monitoring a state of a lubricatable element during a lubricationcycle in which an injection head injects lubricant into the lubricatableelement, comprising: measuring an injection pressure of lubricant beinginjected into the lubricatable element as a function of time during thelubrication cycle; registering the injection pressure as a variablerepresenting the state of the lubricatable element during thelubrication cycle; and evaluating the state of the lubricatable elementas a function of the variable, wherein the injection pressure ismeasured upstream of the injection head as viewed in the direction offlow of the lubricant, and the state of the lubricatable element isevaluated during injection of the lubricant by an analysis of theinjection pressure as a function of time, the analysis including aninterpretation of a pressure increase in the beginning of the lubricanttransfer.
 12. The method as defined in claim 11, wherein the pressureincrease is compared with predetermined minimum and maximum values. 13.A method for lubricating and monitoring a state of a lubricatableelement during a lubrication cycle in which an injection head injectslubricant into the lubricatable element, comprising: measuring aninjection pressure of lubricant being injected into the lubricatableelement as a function of time during the lubrication cycle; registeringthe injection pressure as a variable representing the state of thelubricatable element during the lubrication cycle; and evaluating thestate of the lubricatable element as a function of the variable, whereinthe injection pressure is measured upstream of the injection head asviewed in the direction of flow of the lubricant, and the state of thelubricatable element is evaluated during injection of the lubricant byan analysis of the injection pressure as a function of time, theanalysis including an interpretation of a transfer time, the transfertime defined as a time during which the pressure is substantially equalto constant maximum pressure observed during the injection cycle.
 14. Amethod for lubricating and monitoring a state of a lubricatable elementduring a lubrication cycle in which an injection head injects lubricantinto the lubricatable element, comprising: measuring an injectionpressure of lubricant being injected into the lubricatable element as afunction of time during the lubrication cycle; registering the injectionpressure as a variable representing the state of the lubricatableelement during the lubrication cycle; and evaluating the state of thelubricatable element as a function of the variable, wherein theinjection pressure is measured upstream of the injection head as viewedin the direction of flow of the lubricant, and the state of thelubricatable element is evaluated during injection of the lubricant byan analysis of the injection pressure as a function of time, theanalysis including an interpretation of a transfer time, the transfertime defined as a time during which the pressure is greater than apredetermined percentage of 90% of a maximum pressure observed duringthe injection cycle.